on a street machine, I wouldn`t waste my time trying to make horsepower. Torque is what moves all that sheet metal around, not horsepower. a high torque engine is what makes a car fun to drive, a hole shot that slams you back in the seat, the feeling of how hard it`s pulling under acceleration, how the engine seems to move the car effortlessly, the sensitivity when you just tap the pedal is all by torque. so for the ultimate combo, the most cubic inches is always best. a 383 or a 400 since were talking small blocks, both will make lots of torque, instead of shooting for 450 horse power, why not shoot for 450 ft/lbs of torque? good heads, valve train, a decent compression ratio, a tight quench clearence, a good intake, ignition, exhaust system with decent rear gears all work together to make a good street machine. it`ll also make good horsepower as well. it won`t be near as hard on the engine because you won`t have to rev it to hel* to make power.